The present invention relates to a multistage rolling mill with a mechanism for controlling the flatness of the rolled product.
In recent years, to control the sectional flatness of the rolled product in the width direction, the work roll bending method by a four high mill has been developed, but the roll bending method adopted is limited in the capability of controlling the flatness of the rolled product.
To obtain a rolled product with a good flatness especially with little variation of thickness in the width direction, it is important to keep the deformation of the work rolls by the rolling load, etc. as small as possible and to enhance the capability of correction by roll bending.
A conventional four high mill has only a roll bending device for vertical bending, and for this reason, it allows only a limited crown correction and can correct only a simple parabolic shape. This allows only the flatness correction of edge waves and center buckles and does not provide sufficient capability in controlling complicated ones such as compound waves, etc. Furthermore, for narrow sheets with a width smaller than 1/2 of the roll shaft length, unsatisfactory results in flatness correction are obtained.
In this situation, horizontal bending as shown in FIG. 1 was developed.
In the developed rolling mill, work rolls c and d are properly offset in the rolling direction from the vertical line connecting the centers of backup rolls a and b, and support rolls h adapted to move horizontally are arranged through pressure rolls g against the offset work rolls c and d, to allow the flatnesss control of the rolled product horizontally. In this rolling mill, since the flatness control actuator is engaged in horizontal bending only, the control capability is limited, and since the backup rolls are driven, there is possibility of slipping caused at a high draft. In addition, the exchange of the pressure rolls g and the support rolls h takes much time and needs much effort.
The first object of the present invention is to considerably enhance the capability of the rolling mill in controlling the flatness of the rolled product.
The second object of the present invention is not to lower the workability in roll exchange and maintenance in enhancing the capability of controlling the flatness of the rolled product.
The multistage rolling mill with flatness control function according to the present invention is described below in reference to drawings.